#!/usr/bin/perl -w

use Inline C;
#use Benchmark qw(:all);

local $/=undef;

my $file=$ARGV[0] or die("you must specify a file");
open my $fh, "<", $file;
my $text=<$fh>;
close $fh;

##$stat=timethese(100, {
##	'Perl' => sub { _is_utf8($text); },
##	'InlineC' => sub { __is_utf8($text); },
##});
##cmpthese($stat) ;

if(__is_utf8($text)) { print "\nseems to be utf8\n"; }
else { print "\ndoesn't seems to be utf8\n"; }

sub _is_utf8 {
	my $text=shift;
	my @asc=unpack("C*",$text);
	my $len=scalar(@asc);
	my $i=0;
	my $utflen=0;
	my $c=0;
	#print "PParsing ".$len." bytes\n";
	while($i<$len) {
		$c=$asc[$i];
		if($c & 0x80) { #high bit? => utf char ?
			#print "highbit! [".$c."]";
			if   (($c&0xe0)==0xc0) { $utflen=1; }
			elsif(($c&0xf0)==0xe0) { $utflen=2; }
			elsif(($c&0xf8)==0xf0) { $utflen=3; }
			else { return 0; }
			#print " len=".$utflen;
			while($utflen--) {
				$c=$asc[++$i];
				return 0 if(($c&0xc0)!=0x80);
			}
			#print " ok\n";
		}
		++$i;
	}
	1;
}

__END__

__C__

int __is_utf8(char *txt) {
	unsigned char c;
	int len;
	while((c=*txt++)!=0)
		if((c&0x80)==0x80) {
			if     ((c&0xe0)==0xc0) len=1;
			else if((c&0xf0)==0xe0) len=2;
			else if((c&0xf8)==0xf0) len=3;
			else return 0;
			while(len--) {
				c=*txt++;
				if((c&0xc0)!=0x80) return 0;
			}
		}
	return 1;
}